1. Field of the Invention
This invention relates to a mechanical sealing device and particularly to the technical field of a cartridge type mechanical sealing device adapted to seal high viscosity fluid or slurry contained fluid and prevent solid matters contained in the fluid to be sealed from sticking on the components and clogging between the components.
2. Description of the Related Art
There has been, as a related art, U.S. Pat. No. 4,290,611. FIG. 5 is a half sectional view of the mechanical seal shown in FIG. 4 of U.S. Pat. No. 4,290,611.
In FIG. 5, the reference numeral 100 denotes a mechanical seal. The mechanical seal 100 is comprised of a pair of primary components so as to be attached to a rotary shaft 151 and then installed within a stuffing box 150 through fastening bolts 160. The mechanical seal 100 includes, as the primary components thereof, a liquid sealing device 101, a fist seal flange 110, a second seal flange 120 and a gas sealing device 121 that are arranged in order, from the inside of the stuffing box 150 toward the outside thereof, in the axial direction.
The liquid sealing device 101 is mounted on the outer circumference of a sleeve 153 secured onto the rotary shaft 151 through a screw socket 152. Between the rotary shaft 151 and the sleeve 153 fitting thereto is disposed an O-ring 154 for sealing therebetween.
In the liquid sealing device 101, a rotary seal ring 102 formed with a rotary seal face 103 is resiliently biased by a spring 105 through a U-shaped gasket 107 and a spacer 108.
Also, a stationary seal ring 112 having a stationary seal face 113 in contact with the rotary seal face 103 is fitted to the inner circumference of the first seal flange 110 through an O-ring 116. Further, at least one pin 115 secured to the stationary seal ring 112 engages a groove provided in the inner circumference of the first seal flange 110 to engage the stationary seal ring 112 with the first seal flange 110.
A gas-sealing device 121 is installed inside of the inner circumference of the second seal flange 120 coupled with the first seal flange 110. The gas-sealing device 121 is provided with a drive sleeve 125 that is secured to the sleeve 153 through at setscrew 126. A second rotary seal ring 122 having a second rotary seal face 123 is fitted in the drive sleeve 125 to slide therein. One end of a fluid passage formed in the second rotary seal ring 122 for creating dynamic pressure is opened at the second rotary seal face 123.
A second stationary seal ring 132 having a second stationary seal face 133 in close contact with the second rotary seal face 123 of the second rotary seal ring 122 is fitted to the inner circumference of the second seal flange 120 through an O-ring 136. In the second stationary seal face 133 are formed a plurality of grooves for creating dynamic pressure, in cooperation with the second rotary seal face 123. Also, the second rotary seal ring 122 is resiliently biased by a coil spring 127 toward the second stationary seal ring 132 side.
The second seal flange 120 is provided with a drain tap 128 for draining liquid that leaked from the liquid sealing device 101. Also, in the stuffing box 150 is provided a flushing port 158 for washing the liquid sealing device 101 using liquid ejected therefrom.
The mechanical seal 100 is assembled to the rotary shaft 151 and then the assembly is inserted and installed inside of inner circumferential surface 156 of the stuffing box 150.
The mechanical seal 100 constituted as described is installed, through the sleeve 153, in a space 157 that is formed between the outer circumferential surface of the rotary shaft 151 and the inner circumferential surface 156 of the stuffing box 150. The space 157 is required of a size enough to contain the sleeve 153 and the liquid sealing device 101. However, the increase of the diameter of the inner surface 156 of the stuffing box 150 is often limited due to structural conditions. Accordingly, the gap formed between the inner surface 156 of the stuffing box 150 and the liquid sealing device 101 will be small, which causes the flow of the sealed fluid to be worsened. The rotary seal face 103 and the stationary seal face 113 heated by sliding heat generation cannot be satisfactorily cooled. This causes the seal faces to be damaged.
Additionally, it is difficult to wash the liquid sealing device 101 when a washing liquid is flushed through the flushing port 158.
If the fluid to be sealed is viscosity fluid or slurry contained fluid, slurries contained in the fluid are apt to clog between the liquid sealing device 101 and the inner surface 156 of the stuffing box 150. This causes the cooling effect on both seal faces 103, 113 as well as the sealing ability thereof to worsen, resulting in sealed fluid leakages between the seal faces 103, 113.
Furthermore, there are such problems that erosion or rust occurred in the spring 105 due to direct contact of the spring 105 with the sealed fluid reduces the elasticity thereof and adhesion of the sealed fluid slurry onto the spring 105 causes the operation of the spring 105 to push the rotary seal ring 102 to be deficient. Additionally, since slurries stick between the sliding faces of the rotary seal ring 102 and the sleeve 153 or between the sliding faces of the spacer 108 and the sleeve 153, and then bite into them, the response of the rotary seal ring 102 to the surface pressure is worsened to cause the sealing ability to be reduced.
As has been described, in order to prevent the reduction of the sealing ability of the liquid sealing device 101 it is required to arrange a bilateral sealing device. As a result, the structure becomes complicated and higher accuracy for assembly is required. The complicated structure for the liquid sealing device 101 makes difficult to cool the rotary seal ring 102 and the stationary seal ring 112 and induces thermal deformation of the seal faces 103, 113. As a result, the sealing ability is worsened and the seal surfaces are damaged.
This invention is achieved in view of such problems as described previously, the technical problem to be solved by the invention is to provide a liquid sealing device that is arranged to be mounted outside of the stuffing box and the rotary shaft regardless of the structure of the stuffing box, for allowing the seal faces of the stationary and rotary seal rings sliding each other to be cooled and for preventing slurries in the sealed fluid or high viscosity fluid from sticking to cause the response to be deficient.
Another technical problem to be solved is to easily wash off slurries contained in the sealed fluid or high viscosity fluid that sticks in the liquid sealing device and solidifies, especially wash the sliding faces of the seal rings at any time for maintaining good response of the seal rings to the surface pressure.
A further technical problem to be solved is to provide a sealing device that is arranged to be mounted outside of the stuffing box and the rotary shaft regardless of the structure of the stuffing box, for allowing the distance between the opposing faces of the stationary and rotary seal rings to be enough to avoid any inverse affects from the slurry contained fluid and high viscosity fluid.
A further yet technical problem to be solved is to provide a sealing device having a structure so that fixing pins or the like for preventing the rotation of the seal rings and springs that bias the seal rings are not inversely affected by the sealed fluid.